Dye sensitized solar cell (DSC or DSSC) is pollution-tree clean technology which generates electric power by converting light energy into electrical energy as application of the principle of photosynthesis in plants. It has emerged as a prime alternative to overcome limits of silicon solar cell which occupies most of the current solar cell market.
The characteristics of dye sensitized solar cell are the capability of realizing the various colors by using the variety of dyes, and using effectively the spectrum of sunlight.
In addition, dye sensitized solar cell is formed of porous photocathode layer and therefore exhibits relatively high power generation efficiency for scattered light as well as direct sunlight, resulting in the large amount of power generation.
Dye sensitized solar cell has the structure of nanoparticles adsorbed to transparent electrodes coating a transparent glass, herein the nanoparticle is semiconductor substance, mainly TiO2. The nanoparticle is coated with dye polymer as mono-layer. Principle is that the dye absorbs light, generating electrons, and generated electrons are carried to electrode by nanoparticles resulting in the electric current flow.
In general, electrode of dye sensitized solar cell is prepared by preparing TiO2 nanoparticles, preparing TiO2 nanoparticle paste by adding the solvent to the TiO2 nanoparticles, preparing nanoporous TiO2 layer by applying the TiO2 nanoparticle paste on the substrate and sinitering by heat treatment at the high temperature of around 400-500, and then depositing dye layer on the TiO2 layer by dipping the substrate in dye.
Preparation method of TiO2 nanoparticle based on sol-gel process is the most typical and effective method which prepares nano-size titanium dioxide economically due to a simple process. Nano-size TiO2 can be prepared as the particles with a variety of forms such as spheres, rods, tubes, wires, platelets, porous and aerogel by sol-gel method. The characteristics of prepared titanium dioxide are known to be significantly affected by pH, presence of catalyst, temperature, and the properties of precursor and the like.
TiO2 sol is prepared by dispersing titanium isopropoxide and titanium butoxide of appropriate molar ratio in IPA and adding the mixed solution of H2O, HNO3, IPA followed by reacting. TiO2 sol, prepared as mentioned above, requires the high temperature calcination by high-temperature heat treatment in order to form nanoporous as described above. A high temperature calcination method has high energy cost and accompanies inconvenience in the process.
In addition, the conventional method of preparing electrode for dye sensitized solar cell requires separate dye adsorption process after deposition of TiO2 nanoparticles and therefore accompanies complexity of the process.
In addition, in order to increase the power generation efficiency of the solar cells, it is necessary to improve energy conversion efficiency of titanium dioxide paste for dye sensitized solar cell.
Therefore, the method for preparing low temperature curable TiO2 nanoparticle paste is required. Also, the method for preparing titanium dioxide paste for dye sensitized solar cell, which can improve energy conversion efficiency and requires no separate dye adsorption process, is required.
Under this background, the present inventors identified that low temperature curable paste which is capable of coating without micro-fissure can be prepared by forming —O—Ti—O— network between titanium dioxide nanoparticle and titanium dioxide precursor by inducing the hydrolysis of titanium dioxide nanoparticle and titanium dioxide precursor by mixing titanium dioxide precursor, which can act as a binder, to titanium dioxide nanoparticles dispersed in a solvent at a constant molar ratio to complete the present invention. In addition, it is verified that low temperature curable paste which requires no separate dye adsorption process or can improve energy conversion efficiency by adding dye or metal precursor in advance can be prepared.